The present invention relates to a method and apparatus for fillet formation under the head of a metal pin type fastener.
Metal fasteners of a pin type such as bolts, pins, rivets and the like are routinely formed with an elongated shank and an enlarged head at one end. In order to reduce any stress concentration at the juncture of the shank and head, a fillet radius is formed at that connection. With fasteners that are used to secure workpieces with a high clamp force the tensile load between the head and the shank can be significant. Thus it is desirable that the fillet radius at that juncture be well formed and of sufficient strength. It is common for a pin blank to be first formed by a cold or hot heading operation whereby the head is formed at one end of the shank. In the heading process a fillet radius is routinely formed at the juncture between the shank and the enlarged head. In addition it is not uncommon to perform a subsequent grinding step in which the fillet is also ground. Such fillets, however, when formed by heading and/or grinding may have certain inconsistencies in geometry, hardness and grain structure. It is also common to heat treat the pin blank to substantially remove variations in hardness and grain structure. It has also been common to attempt to remove geometric inconsistencies and increase fillet hardness by a subsequent rolling operation. In this regard, the hardness of the fillet is increased by cold working in rolling.
However, even here, with conventional rolling apparatus, there can be inconsistencies in the rolling process caused by variations in force or pressure, rolling speed and time or number of revolutions, shank diameters, head geometry, etc. In this regard variations in shank diameters, head geometry, etc. where the wrong blanks are fed for rolling may not be recognized. At the same time, such apparatus for rolling is not particularly versatile and can require substantial time for set up, modification for different diameters, different head styles, i.e. flush type or protruding type, blanks of different materials, etc. In addition the metallic pins are conventionally made of alloys of titanium, steel, aluminum and the like which can require different parameters for fillet rolling.
In this regard, it should be noted that with current, conventional rolling apparatus it is common to have the rollers oriented in a vertical plane with the input opening for receiving the pin blank to be rolled extending along a horizontal axis. Here the pin blank to be rolled may be fed down a slide and inserted horizontally into the input opening. It is also common to have the rollers oriented in a horizontal plane. Here the pin blank may be fed down a slide to a feed arm which will grip the pin blank and then move to a position to insert the pin blank vertically into the input opening. It is also common for the roller subassemblies to be moved radially in translation to enlarge the opening to facilitate insertion of the pin blank by the feed arm and then to close the opening for rolling.
As will be seen one of the unique features of the present invention locates the rollers in a horizontal plane with the input opening extending along a vertical axis. Here, however, the pin blank to be rolled is dropped vertically down a slide into the input opening with the natural assistance of gravity and without the need for a feed arm.
In addition, the structure for handling the pin blank for insertion for rolling and ejection after rolling is highly efficient whereby the overall cycle time for processing the pin blanks for rolling is reduced. In this regard the amount of rolling time can be increased while still resulting in a reduction in the overall cycle time. The increased rolling time can assist in providing more consistently rolled fillets.
Thus the present invention provides a unique method and apparatus for addressing the above problems while at the same time providing a relatively simple, quick means for the accurate set up and adjustment of the fillet rolling apparatus for operation. In addition the unique method and apparatus monitors various parameters of the process to provide a consistent, uniformly formed fillet radius on a preselected form of pin blank. At the same time, blanks rolled with the wrong parameters will be detected and rejected. This also results in the form of the pin blank being indirectly monitored to reject blanks of the incorrect form which will not attain the noted parameters in fillet rolling.
Another feature of the present invention is that various ones of the combination of elements of the rolling apparatus are of known structures but which have been readily modified or adapted to provide the unique combination of the present invention.
Thus it is an object of the present invention to provide a unique rolling method and apparatus for fillet formation at the juncture of the shank and head of pins, bolts and the like.
It is another object to provide such a unique rolling method and apparatus which facilitates adjustment to accommodate for differences in sizes, shapes, the fillet radius, materials, etc. of the pins, bolts and the like.
It is still another object to provide a unique rolling method and apparatus whereby the overall processing time per pin blank is minimized.
It is also an object of the present invention to provide a unique rolling method and apparatus in which the rollers are oriented horizontally with the input opening for receiving the pin to be rolled extending along a vertical axis whereby the pin to be rolled is inserted vertically by gravity.
It is still another object of the present invention to provide a unique method and apparatus for fillet rolling which monitors the significant factors involved in rolling such as applied load or force on the pin, bolt and the like during rolling, the size of the pin shank, type of pin head, the proper or improper application of steps in rolling and the like.
Thus the present invention provides a unique rolling apparatus and method for forming and working of the fillet radius at the juncture of the shank and enlarged head of pins, bolts, rivets and the like. The rolling apparatus and method facilitates set up and adjustment while monitoring various factors relating to the consistency and quality of the rolled fillets.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.